Submersible pumps for use in a borehole are known from the prior art, for example as NSPCP (Netzsch submersible PCP=submersible eccentric screw pump from Netzsch) or ESPCP (=electrical submersible eccentric screw pump). In these submersible pumps, a submersible motor present at the lower end is provided, which by means of a coupling rod drives an eccentric screw pump located above. Compared with the conventionally used centripetal pumps, the use of eccentric screw pumps has the advantage that products with higher viscosity, for example with higher sand and paraffin components, can be delivered.
In order to be able to take up the axial force resulting from the delivery pressure, a bearing arrangement for bearing the coupling rod is usually disposed directly above the submersible motor or above a gear unit connected to the submersible motor.
DE 10258666 A1 describes a submersible pump arrangement for use in a borehole with a screw or eccentric screw pump, wherein a coupling part taking up axial and radial forces is disposed between the slowly rotating drive and the screw or eccentric screw pump.
DE 19848792 C1 describes a submersible pump arrangement for use in a borehole, which comprises a gear unit and a compensator between the drive and the eccentric screw pump. A gear stage serves to slow down the rotary motion of the input shaft in the gear housing. The compensator brings the lubricating fluid pressure in the gear housing into line with the ambient pressure. In order to distribute the arising heat of the gear stage uniformly over the lubricating fluid, the compensator is disposed inside the gear housing beside the gear stage and is integrated into the lubricating fluid circuit.
An essential drawback with these arrangements consists in the fact that slender and rapidly running coupling rods between the drive and the screw or eccentric screw pump have a tendency to buckle easily on account of the prevailing axial force and then run against the housing pipe. This leads to friction between the coupling rod and the housing pipe and therefore to wear of these components, which accordingly often have to be exchanged or replaced.
The problem of the invention consists in overcoming the drawbacks of the prior art, in particular the buckling of the coupling rods due to axial forces acting on the coupling rods is to be prevented.
The above problem is solved by a submersible pump assembly which comprises the features described in the independent claim. Further advantageous embodiments are described in the sub-claims.